Alaska is surrounded by approximately 44,000 miles of coastline (including bays and fjords) and is covered by about 86,000 square miles of water. Alaska's dynamic riverine and coastal environments are vulnerable to geologic hazards because they can change rapidly in response to natural forces and human activities. Coastal and river hazards can result from storm and tidal surges, tsunamis, ice jams, ice impacts and unusually fast thaws in high snow years. Resulting impacts include flooding, erosion and damage to infrastructure.